This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2001-367754, filed Nov. 30, 2001; No. 2001-367755, filed Nov. 30, 2001; and No. 2001-367941, filed Nov. 30, 2001, the entire contents of all of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a magnetic random access memory (MRAM) in which a memory cell is constructed using MTJ (Magnetic Tunnel Junction) elements having xe2x80x9c1xe2x80x9d, xe2x80x9c0xe2x80x9d-information stored therein by a tunneling magneto resistive effect.
2. Description of the Related Art
In recent years, there have been proposed many memories having information stored therein by new principle, and one of them is a memory using a tunneling magneto resistive (hereinafter, denoted as TMR) effect proposed by Roy Scheuerlein et. al (for example, refer to ISSCC2000 Technical Digest p. 128 xe2x80x9cA 10 ns Read and Write Non-Volatile Memory Array Using a Magnetic Tunnel Junction and FET Switch in each cellxe2x80x9d).
The magnetic random access memory stores xe2x80x9c1xe2x80x9d, xe2x80x9c0xe2x80x9d-information by the MTJ elements. The MTJ elements have a structure in which an insulation layer (tunnel barrier) is sandwiched with two ferromagnetic layers. The information stored in the MTJ elements is determined by whether or not the orientations of spins of the two ferromagnetic layers are parallel or anti-parallel.
Here, parallel means that the orientations of the spins of the two ferromagnetic layers are same, and anti-parallel means that the orientations of the spins of the two ferromagnetic layers are opposite to each other.
Generally, one of the two ferromagnetic layers constructing the MTJ element is a pin layer in which the orientation of the spin is pinned. When xe2x80x9c1xe2x80x9d, xe2x80x9c0xe2x80x9d-information is stored in the MTJ elements, the orientation of the other one (free layer) of the two ferromagnetic layers is varied according to written information.
A magnetic random access memory according to a first aspect of the present invention comprises: first and second MTJ elements each configured with a first magnetic layer in which the orientation of a spin is pinned, a second magnetic layer in which data is stored, and an insulation layer sandwiched between the first and second magnetic layers; and a first write line which is arranged between the first and second MTJ elements and generates magnetic fields acting on the first and second MTJ elements. A positional relationship between the first magnetic layer, the insulation layer, and the second magnetic layer constructing the first MTJ element and the first magnetic layer, the insulation layer, and the second magnetic layer constructing the second MTJ element is symmetric to the first write line.
A magnetic random access memory according to a second aspect of the present invention comprises: an array having a plurality of MTJ elements accumulated in a plurality of portions; a first conductive line arranged in the array; and a second conductive line arranged in the array which has the same function as the first conductive line and is arranged above the first conductive line, wherein the first and second conductive lines are connected in serial.
A magnetic random access memory according to a third aspect of the present invention comprises: an array having a plurality of MTJ elements accumulated in a plurality of portions; and a first write line which extends in the direction in which the plurality of MTJ elements are accumulated and is provided for generating a magnetic field during writing.